Light Emitting Device Array Billboard and Control Method Thereof

1. A light emitting device array billboard, comprising: a light emitting device array including a plurality of light emitting devices arranged by a plurality of lines and a plurality of channels, wherein in each line, a forward end of each light emitting device is coupled to a common line node, and in each channel, a reverse end of each light emitting device is coupled to a common channel node; a plurality of line switch circuits respectively coupled to the corresponding line nodes, for electrically connecting the corresponding line nodes to a conduction voltage or a discharge path according to a line operation signal; a plurality of channel switch circuits each of which includes a corresponding current source, the channel switch circuits being respectively coupled to the corresponding channel nodes, for electrically connecting selected ones of the channel nodes to corresponding current sources according to a channel operation signal; a plurality of ghost image compensation switch circuits respectively coupled to the corresponding channel nodes, for electrically connecting selected ones of the channel nodes to a ghost image compensation voltage according to a ghost image compensation signal; and a control circuit coupled to the line switch circuits, the channel switch circuits and the ghost image compensation switch circuits, for providing the line operation signal, the channel operation signal and the ghost image compensation signal; wherein the control circuit provides the line operation signal and the channel operation signal to respectively control the line switch circuits and the channel switch circuits such that a selected one of the light emitting devices is turned ON for a duty period within a lighting period, and the control circuit provides the ghost image compensation signal to control the ghost image compensation switch circuits such that the channel node corresponding to the selected one of the light emitting devices is electrically connected to the ghost image compensation voltage when the selected one of the light emitting devices is not conductive after the lighting period; and wherein the control circuit further adjusts the channel operation signal according to a gray scale compensation signal such that the selected one of the light emitting devices is turned ON for a gray scale compensation period in addition to the duty period.

2. The light emitting device array billboard according to claim 1 , wherein each of the line switch circuits includes: a first switch coupled to the corresponding line node, for electrically connecting the corresponding line node to the conduction voltage according to the line operation signal; and a second switch coupled to the corresponding line node, for electrically connecting the corresponding line node to ground or a relatively lower potential according to the line operation signal, for providing the discharge path.

3. The light emitting device array billboard according to claim 1 , wherein each of the channel switch circuits includes: a third switch coupled to the corresponding channel node, for electrically connecting the corresponding channel node to the current source according to the channel operation signal; and the current source, coupled to the third switch, for providing a light emitting device current to the selected one of the light emitting devices.

4. The light emitting device array billboard according to claim 3 , wherein the control circuit further provides an adjustment signal according to the gray scale compensation signal to adjust the light emitting device current in the gray scale compensation period.

5. The light emitting device array billboard according to claim 1 , wherein the ghost image compensation voltage is higher than a voltage which is equal to the conduction voltage minus a forward bias voltage of the light emitting device.

6. The light emitting device array billboard according to claim 1 , wherein the control circuit further adjusts the channel operation signal according to the gray scale compensation signal such that the non-selected light emitting devices are not turned ON in the lighting period and the gray scale compensation period.

7. A method for controlling a light emitting device array billboard which includes a plurality of light emitting devices arranged by a plurality of lines and a plurality of channels, wherein in each line, a forward end of each light emitting device is coupled to a common line node, and in each channel, a reverse end of each light emitting device is coupled to a common channel node, the method comprising: selecting at least one of the light emitting devices; electrically connecting the line node corresponding to the selected one of the light emitting devices to a conduction voltage or a discharge path according to a line operation signal; electrically connecting the channel node corresponding to the selected one of the light emitting devices to a current source according to a channel operation signal; electrically connecting the channel node corresponding to the selected one of the light emitting devices to a ghost image compensation voltage according to a ghost image compensation signal, whereby the selected one of the light emitting devices is turned ON for a duty period within a lighting period according to the line operation signal and the channel operation signal, and the channel node corresponding to the selected one of the light emitting devices is electrically connected to the ghost image compensation voltage according to the ghost image compensation signal after the lighting period; and adjusting the channel operation signal according to a gray scale compensation signal such that the selected one of the light emitting devices is turned ON for a gray scale compensation period in addition to the duty period.

8. The method for controlling a light emitting device array billboard according to claim 7 , wherein the ghost image compensation voltage is higher than a voltage which is equal to the conduction voltage minus a forward bias voltage of the light emitting device.

9. The method for controlling a light emitting device array billboard according to claim 7 , further comprising: providing an adjustment signal according to the gray scale compensation signal to adjust a current of the selected one of the light emitting devices in the gray scale compensation period.

10. The method for controlling a light emitting device array billboard according to claim 7 , wherein the non-selected light emitting devices are not turned ON in the lighting period and the gray scale compensation period.